An optical network provides the functionality of communicating traffic of a client device through an optical fiber communication channel to establish a connection between hubs. The optical network receives a client signal through an interface between a node device and the client device. A plurality of client signals are multiplexed in a variety of multiplexing schemes, and then the multiplexed client signals are communicated through an optical fiber communication channel having a larger capacity. The multiplexing schemes include a wavelength division multiplexing (WDM) scheme, a time division multiplexing (TDM) scheme and the like.
In such an optical network, a small-granularity switching device such as a switch and a router concentrates a plurality of client signals in accordance with demand traffic of the client device. In order to accommodate the plurality of concentrated client signals with high efficiency in an optical path by which communication is performed through an optical fiber communication channel, a traffic grooming technology is required that is a technology to concentrate a plurality of client signals passing through a common optical fiber communication channel.
Patent Literature 1 discloses an example of such a technology to accommodate a line concentration signal obtained by performing line concentration on a plurality of client signals in a wavelength path of an optical network.
A related path accommodation design apparatus described in Patent Literature 1 is composed of a sub-λ path setting request obtaining section, a design section, a network information management section, and an operation result storage section. The design section includes a logical route determination functional section, a physical route determination functional section, a wavelength use rate computation functional section, a wavelength allocation determination functional section, a sub-λ path accommodation functional section, and an operation rate computation functional section.
The design section accommodates a sub-λ (electric) path in a wavelength path in the following order (priority). That is to say, the design section accommodates the sub-λ path, first, in an existing wavelength path of a single-hop logical route, second, in an existing wavelength path of a multi-hop logical route, third, in a new wavelength path of a single-hop logical route, and fourth, in existing and new wavelength paths of a multi-hop logical route. In this case, if there are a plurality of candidates for the same priority, a candidate having the smallest number of hops for the physical route is selected. If there are a plurality of routes having the same number of hops for the physical route, one of the routes that has the smaller number of hops for the logical route is selected. Furthermore, if there are a plurality of routes having the same number of hops for the logical route, one of the routes that has a smaller wavelength use rate computed by the wavelength use rate computation functional section is selected.
If a redundant path is designed, the logical route determination functional section computes a plurality of candidate logical routes and computes possible combinations between N paths as redundant paths. In this case, each combination is deleted in which the operation rate for the logical route computed by the operation rate computation functional section does not satisfy the quality requirement; alternatively, each combination having node overlapping is deleted.
Next, the physical route determination functional section computes candidate physical routes for the combinations of the computed logical routes. In this process, for each computed logical route that passes a relay node, a route that does not pass the relay node is deleted. In this case, similarly, each combination in which the operation rate does not satisfy the quality requirement is deleted; alternatively, each combination in which the node overlapping, link overlapping, pipeline overlapping, or the like occurs is deleted.
Next, the logical route design functional section computes a logical route that has a free band equal to or wider than the request band and thus has a high accommodation efficiency in the above-mentioned order. The design section then determines whether it is possible to accommodate a sub-λ path in the wavelength path with the computed logical route. If it is determined that the accommodation is possible, the sub-λ path accommodation functional section accommodates the sub-λ path in the wavelength path.
According to the related path accommodation design device, the above-mentioned configuration makes it possible to perform path accommodation design that produces no uneven route arrangement, improve traffic accommodation efficiency, and design highly reliable redundant routes.
On the other hand, in order to use optical frequency resources effectively, an elastic optical network scheme is proposed (see Patent Literature 2, for example). In the elastic optical network scheme, it is possible to allocate a minimum frequency band in accordance with the transmission capacity of an optical signal to a route between the nodes to send and receive an optical signal on a network in which a plurality of nodes are connected by optical fibers. The elastic optical network scheme makes it possible to determine flexibly a frequency band to be allocated by the number of slots using a predetermined frequency width as one slot section.
As described above, according to the elastic optical network scheme, it is possible to change the number of the required wavelength slots of an optical path depending on the required traffic capacity. This makes it possible to allocate an optical path to surplus wavelength resources that cannot be utilized in the conventional fixed grid network; accordingly, it becomes possible to improve the utilization efficiency of the optical network.